KM35P Transmission is thumping in low gear

[bchbum1972]

I need help on how to proceed.

I have a Yanmar 4JH4AE with a Kanzaki transmission making a thumping in low rmp the does go away in high gear. I ran into a crab trap some time ago and noticed the engine is out of alignment by looking at the mounting bolts and also confirmed by checking the coupler witch has a gap big enough to fit a playing card through. .22 mm or so.

My question is when I checked the transmission by disconnecting from the shaft all seems well ... and it shift smoothly. Should I just realign the engine and pray all is good or is there some internal damage to transmission i need to be worried about. I really dont have the cash to for a new transmission. Any help would be greatly appriciated

Thank you
James

[Calif.Ted]

I believe I'd realign and dive to check your shaft, cutlass and strut are free of rope and crap, and strut hasn't been damaged or moved. Last time I got tangled in some discarded fishing gear there was poly rope, pieces of wood used as floats and lead weights tangled in my running gear.

[SVHarmonie]

If the engine is visibly out of alignment, OF COURSE you have to fix that! FIRST. Running an engine out of alignment WILL destroy bearing and seals in the transmission. Until everything is aligned properly you really don't know what's wrong.

One possible cause for a thumping noice at low rpm that disappears at high speed is a failure in the damper plate that connects the transmission to the engine. But save worrying about that until you have things back straight.